Isolation and characterisation of stress compounds produced by marine sponge bacteria

• Main Author: Chow, Lai Theng
• Format: Thesis
• Language: English; English
• Published: 2016
• Subjects: QR75-99.5 Bacteria
• Online Access: https://eprints.ums.edu.my/id/eprint/39376/1/24%20PAGES.pdf; https://eprints.ums.edu.my/id/eprint/39376/2/FULLTEXT.pdf; https://eprints.ums.edu.my/id/eprint/39376/

In order to cope with the imbalanced nutrient growth conditions, stress compounds are commonly synthesised by bacteria as the strategy of survival. Examples of bacterial stress compounds are polyhydroxyalkanoate (PHA), triacyglycerol (TAG) and wax ester (WE) inclusions. However, there has not been any prior report on marine stress compounds-producing bacteria isolated from sponges. Hence, present investigation looks into the isolation and identification of stress compounds-producing bacteria from marine sponge. Structural elucidation of the extracted stress compounds was also studied. In an attempt to isolate stress compounds-producing bacteria from marine sponge, Halichondria sp. and Epipolasis sp. were collected from Mantanani Island. Halichondria sp. leads to 15 isolates of marine bacteria, while Epipolasis sp. yielded a total of 42 strains of bacteria. One-step batch cultivation was performed for each of the strains. One bacterial strain, isolate HSP101R2-7 from Halichondria sp. and two strains from Epipolasis sp.: ESP101R3-6 and ESP101R2-12 were detected to possess the ability to accumulate stress compounds by phase contrast microscopy and Nile red staining. The effect of cultivation period and carbon sources was then evaluated by culturing the strains in the mineral salts medium (MM) with different types of carbon sources such as fructose, glucose, sucrose, fish cod liver oil (RCLO) and commercial fish cod liver oil (CFCLO). The incubation time was set to 48 hours, 72 hours and 96 hours. High yield of stress compounds as much as 3.6 mg/mL was extracted from isolate HSP101R2-7 isolated from Halichondria sp. This strain was identified as Gordonia terrae using Gram staining and 16S rDNA analysis. This is the first report on the isolation and identification sponge-derived bacteria with the ability to synthesise stress compounds under nitrogen-limitng growth condition. Nuclear magnetic resonance (NMR) was used to identify the structure of the stress compounds and TAG was confirmed as the only type of stress compound accumulated by Gordonia terrae. TAG inclusions appeared as spherical, clear-edged and surrounded by a layer of membrane based on the TEM micrograph. In addition, the purified TAG was subjected to gel permeation chromatography (GPC) and differential scanning calorimetric (DSC) analysis to study the material properties. Result showed that purified TAG has low thermal stability.